416 ANNUAL KEPORT SMITHSONIAN INSTITUTION, 193 8 



Table 4 



These results indicate that the difference in toxicity is qualitative 

 as well as quantitative. 



Toxicity of baby spiders. — The eggs of the black widow spider hatch 

 within the egg sac, and there the spiderlings undergo their first molt. 

 It seemed interesting to compare the toxicity of the baby spiders with 

 the eggs from which they came, therefore spiders 7 to 10 days after 

 their emergence from the egg sac were studied, as it was thought that 

 much of the material from the egg would by that time have been 

 utilized. Since it was impossible to dissect out the glands, the spiders 

 were macerated in saline, the debris filtered off, washed in fresh saline 

 and the washings added. Undoubtedly many of the venom glands 

 would not be crushed in this process and the toxicity indicated in 

 table 6 resides in the tissue fluids of the spiders and possibly in 

 unabsorbed egg material. 



Table 5 



Average length of venom glands: 



Mature females 



Immature females 



Mature males 



Mm 

 1.75 

 .75 

 .75 



Table 6 



Degree oj exhaustion following biting. — As previously mentioned, 

 other workers have studied the toxic effects of the venom by causing 

 spiders to bite their victims. Among others, Baerg (1922) describes 



